Set Me Up!!!!

[davis7210]

Here are some pics, what do you think? To high to low i have 2 holes left to raise motor?

 

[tashasdaddy]

Re: Set Me Up!!!!

if your computer is set up to resize , or upload to photobucket, and post thumbnails, which we can clik on the enlarge.

you can up load to a free service like photobucket.com then you choose the pictures you want( clik the little box at the bottom left of the picture) scrool to the bottom of the page, clik generate html, it will take you to the next page, scroll down to thumb nails clik on that and copy, then insert it into your post.

also if you are planing on posting pictures, you can use the Blue post reply or the go advanced, manage attachments, there you can upload , directly from your computer. besure you pictures have been resized to fit the format. 640x480 max.

 

[tashasdaddy]

Re: Set Me Up!!!!

i think i would try it there, the way the hull is shaped. then maybe up one hole.

 

[tmcalavy]

Re: Set Me Up!!!!

Ditto, kinda hard to see in those small pix. But looks pretty close. Rule of thumb is you want the cavitation plate (the plate right above prop) even with the bottom of the boat...an inch either way doesn't hurt anything though. Slick lookin rig...what size/brand outboard is it? How does she float and scoot?

 

[davis7210]

Re: Set Me Up!!!!

Thanks, it's a1983 hydra-sport with a 1983 johnson V4 90hp. Not real fast about 40, turning 5000 rpm. new prop on the way will find out then when it turns some R's!! Will try at this height and move up if needed.

 

[tashasdaddy]

Re: Set Me Up!!!!

you need to be turning 5500- 5600.

 

[Dhadley]

Re: Set Me Up!!!!

That motor needs to be at 5800 with an averager load with today's (87 octane) fuel.

There is no set height, it all depends on prop and hull design and how well they work together. It's really hard to tell which model prop that is or how much wear it's got. We do know it's not a Raker or a Turbo Lightning Jr. If we knew the pitch we could figure the % of slip. That'd be a great starting point.

Even if that's an SST II the motor looks low. It looks more like an aluminum prop with very little rake.

 

[davis7210]

Re: Set Me Up!!!!

Good eye, just original 12.75x21 alum. Turning 5000rpm's WOT now, new 13.25 x 17 in the mail!! alum also, just tuning for good overall performance. We'll see what it does and will let you know. Thanks again for all replies VERY GOOD forum!!!!!!! By the way, dhadley are you into boat racing ? you seem to have alot of knowledge .

 

[Dhadley]

Re: Set Me Up!!!!

Let us know how it works. Let's not get our hopes up too high but just realize the more testing we do the better off we are. We'll just keep in mind we're testing aluminum props. Stainless props should have less slip.

As for racing, yes - been around a lap / round or two.

 

[DJ]

Re: Set Me Up!!!!

Good eye, just original 12.75x21 alum. Turning 5000rpm's WOT now, new 13.25 x 17 in the mail!! alum also, just tuning for good overall performance. We'll see what it does and will let you know. Thanks again for all replies VERY GOOD forum!!!!!!! By the way, dhadley are you into boat racing ? you seem to have alot of knowledge .

Whoa! 5K is way to slow. As stated earlier, 5500 is a minimum. As DH said, 5800 is better.

 

[jay_merrill]

Re: Set Me Up!!!!

Am I mistaken about the OMC recommended WOT for this motor? I believe it is 4,500 to 5,500 rpm. Why all the recommendations to run it faster than OMC suggests?

 

[HighTrim]

Re: Set Me Up!!!!

Those suggestions were from 1984. And as stated, is a minimum. For one thing, the fuel is much different now.

 

[Dhadley]

Re: Set Me Up!!!!

That rpm range is where it's rated at as far as horsepower. It doesn't have a lot to do with where the motor will live the longest. It does have a lot to do with the NMMA guidelines for advertised horsepower.

 

[jay_merrill]

Re: Set Me Up!!!!

I'm still confused. OMC rates its motors at a specific rpm, not a range. For example, my motor is rated at 65hp at 5,000 rpm. The rpm range of 4,500 - 5,500 for my motor is specifically described as WOT operating range in the factory maintenance manual.

Here's what the manual has to say about prop selection:

"Selection of the correct propeller is one of the most critical factors in acheiving satisfactory performance of boat and motor. Propellers must be custom selected to match the boat, load or application. (SELECTION OF AN INCORRECT PROPELER CAN CAUSE SERIOUS DAMAGE TO THE MOTOR)"

"Select a propeller that will allow the motor to run at the top limit of its full throttle operating range with the lightest load that the boat will carry. (see Specifications, Section 2, Full Throttle Operating Range.)"

"Remember, if the motor operates below the recommended full throttle RPM range, motor is laboring and power and efficiency are being lost. If the motor operates above the recommended full throttle RPM range, motor speed is excessive and additional power and efficiency are not being gained. In either case, serious engine damage may result."

My concern here is that the advice being given will result in excessive stress and wear on the OP's engine. That said, I'm all ears if someone has some data, resulting from long term testing, that indicates there is some benefit to running the motors faster than OMC recommends.

 

[wilde1j]

Re: Set Me Up!!!!

Forget the owner's manual. 5800 is the target number, that is unless you don't care how long the motor will last. OMC and BRP have shown numbers that are way too low for V4 and V6 motors.

 

[Dhadley]

Re: Set Me Up!!!!

Do some testing on your own. Set your boat up at 5000 and see how long it takes for the rings to coke up. (Don't go too long, the rings will break) Then decarb and set it up at 5500. Now how long? Decarb and set it up at 6000. Now how long?

Or look for threads here about broken rings. Notice how they're almost always on the starboard side (V motors)? Notice how all the motors are set up in the low 5000 range? Ever seen a performance motor with coked up or broken rings?

 

[jay_merrill]

Re: Set Me Up!!!!

Forget the owner's manual. 5800 is the target number, that is unless you don't care how long the motor will last. OMC and BRP have shown numbers that are way too low for V4 and V6 motors.

I'm going to keep asking, not because I am trying to prove a particular point, but because I am curious. What do you base this on? Why would a motor last longer by being run above the manufacturers recommendations? What does the difference in today's fuels have to do with "saving" a motor by running it faster? I can accept that manufacturers tend to be conservative about such things but, absent information other than opinion, I find it hard to just take the information as "gospel."

PS: Just saw the post about ring problems. That helps and I will look into it.

PPS: DHadley, here is something that you wrote in a outboardrepairs.com thread in 2002:

"The Pennzoil synthetic blend is an excellent oil. We ran engine tests with this oil a few years ago. Carbon and coking were VERY minimal even in a "lugged" set up. Bearings, rod/crank journals and piston skirts were like new after 500 running hours. We used 87 octane fuel, no additives (ring free - carbon guard, ect.) and did not decarbon.

We just completed a 100 hour test using this oil on a V6 cross flow. There was a perfect carbon pattern on the domes and nothing below the top edge of the piston. No sticking rings (coking). This motor was set up to turn only 5000 RPM (stress) with an light load.

We also just went thru a highly modified looper that runs on this oil. Same thing -- insides were perfect."

I happen to use the Pennzoil and I am currently set up at 5,000 WOT rpm at my typical operating weight, with a 15" wheel. Has your opinion changed based on further testing?

 

[Dhadley]

Re: Set Me Up!!!!

Using good oil will help, no doubt. Lugging the engine at 5000 is hurting it internally from the increased combustion temps. Depending on which pistons you have - and therefore what style rings you have - some will coke up faster than others. But the one thing they all have in common is combustion temp. The more you lug it at wot, the higher the temps are regardless of cruise rpm.

 

[davis7210]

Re: Set Me Up!!!!

Here are the real numbers!!!!!! On the very choppy water today got the old girl up to a respectable 44.1 mph GPS . She was turning 5600rpm's WOT! I made appox. 15, 1/2mile runs doing alot of triming. I could trim way up without blowing out. I think maybe up one hole on motor height may help? What do you guys think? New prop got me 600 rpm, pretty close to what i expected. And the best thing was hearing that V4 sounding off!!!!! Man do all johnson's sound that Good? I really appreciate all replies, i am learning so much here!!

 

[Dhadley]

Re: Set Me Up!!!!

The rule of thumb is that if you can use 100% of your trim range you're probably too low for that particular prop on that particular hull with that particular balance. Go up young man, go up.